Method and device for gas cleaning or gas cooling

ABSTRACT

In a method for cleaning polluted gas and/or cooling of hot gas, and a device for carrying out the method, the gas is contacted with finely divided liquid. The finely divided liquid is supplied in the form of essentially umbrella-shaped shells or essentially linear curtains, in a regular arrangement, distributed in two or more planes substantially perpendicular to the main flow direction of the gas. The finely divided liquid is supplied such that the gas is alternatively concentrated and spread by the impulse action exerted by the liquid on the gas in directions perpendicular to the main flow direction of the gas. The orthogonal distance between adjacent planes in which finely divided liquid is supplied, is so adjusted that no substantial equalization of the gas flow takes place between the planes. The supply of liquid in adjacent planes is so arranged that it, in a plane located downstream in the flow direction of the gas, takes place where the flowing gas has been concentrated by the impulse action of liquid supplied in the plane located immediately upstream.

TECHNICAL FIELD

The present invention relates to a method for cleaning polluted gas andor cooling of hot gas, wherein the gas is contacted with finely dividedliquid for the separation of particles or absorption of gaseouspollutants or cooling of the gas. The finely divided liquid is suppliedin the form of essentially umbrella-shaped shells or essentially linearcurtains, in a regular arrangement, distributed in two or more planessubstantially perpendicular to the main flow direction of the gas. Thepresent invention also relates to a device for carrying out the method.The device comprises an inlet for polluted and/or hot gas, an outlet forcleaned and/or cooled gas, and a contact section located therebetween.The contact section accommodates a plurality of supply means providedfor injecting finely divided liquid and arranged in two or more planessubstantially perpendicular to the main flow direction of the gas.

The solution to the technical problem contemplated in the presentapplication can be applied to gas cleaning devices, so-called scrubbers,and gas cooling devices, such as conditioning towers and heat recoveryapparatuses, of most conceivable sizes. The highest demands and thusalso the most important applications, however exist in large industries,large power plants or large incineration plants. In the followingdescription, it is therefore assumed that the devices are on anindustrial scale where the gas washing towers may have a diameter ofabout 1-20 m, and a height of about 1-40 m. For the sake of conveniencethe term "washing" will be used in the following as meaning eithercleaning or cooling or both cleaning and cooling.

The method is applicable only to open gas washing towers. So-calledpacked scrubbers or packed columns cannot be used as contact section inthe method of the invention. However, in a cascade-connectedarrangement, it is of course possible to use a combination of thesuggested washing method and, for instance, packed columns.

The method is especially well suited in contexts where gas cleaning isto be carried out in combination with the recovery of heat from apolluted hot gas, since the good contact between the liquid and the gasalso promotes heat transfer.

TECHNICAL BACKGROUND

Cleaning of polluted gas with a view to removing particulate or gaseoussubstances is an important and common process in today's industrializedsociety. A vast variety of techniques have been developed, and todaythere are often several methods to choose between when a gas cleaningplant is to be designed, even when very specific pollutants are to beremoved.

Particulate pollutants are often removed by means of dynamic separators,such as cyclones, electrostatic precipitators or barrier filters, bagfilters or cassette filters.

Gaseous pollutants are generally removed by the roundabout technique ofusing some additive for convening the gases into particulate substances,either by binding them to the surface of particles supplied, dry or wet,or by reacting them with substances supplied, also in gaseous or liquidform, so as to obtain a particulate product. The reaction product isthereafter separated in a particle separator.

Cooling gas with a view to adapting its temperature or recovering heattherefrom is also nowadays an important and common process. Heattransfer generally takes place either by means of heat exchangers ofrecuperative or regenerative type or by direct contact between the hotand the cold medium. Since this invention concerns heat transfer bydirect contact between a gas and a liquid, other techniques will not bediscussed.

One method which is advantageous in many respects consists in conductinga gas through a rain of finely divided liquid or past surfacesoverflowed by a liquid. These methods make it possible to cool a hot gasas well as to capture particles in the liquid and to dissolve gaseouscomponents of a polluted gas in the liquid. The liquid may then alsocontain substances convening the dissolved gaseous components into solidform in order to make it easier to separate them from the liquid.

The liquid is normally recycled in the washing device, but a portionthereof is removed, generally continuously, in order to use its heat inother applications or to be subsequently treated for separatingpollutants, either in gaseous form or in solid form, optionally forrecovering the substances, and the thus cooled or in other way treatedliquid can be recycled to the gas washing plant to be used again.

These gas washing plants can roughly be divided into open towers wherethe gas only encounters a finely divided liquid, and packed scrubbers orpacked columns where the gas flows through a tower filled with e.g.saddle-shaped or coil-shaped, small parts, on to which liquid is sprayedso as to produce a liquid film which flows downwards over essentiallythe entire total surface.

Since packed scrubbers do not fall within the field of application ofthe present invention, they will not be discussed here.

Examples of open towers, e.g. for separating sulphur dioxide and coolinga gas in order to recover heat, are given in e.g. U.S. Pat. No.3,532,595, where both vertical towers and scrubbers with horizontal gasflow are disclosed and liquid is supplied at several levels orpositions. U.S. Pat. No. 4,164,399 describes a tower of less complexdesign, where liquid is supplied only at one level but is distributedafter being captured at several levels. U.S. Pat. No. 2,523,441 shows acombination of an open tower with a packed section.

The above-mentioned techniques substantially require that the liquidused in the gas washer, during the major part of its movement in thetower, falls or flows downwards by gravity. It is however also known todesign scrubbers which generate more or less horizontal liquid curtainsthrough which the gas is flowed. One example of this is found in thehighly complex design disclosed in SE-103,474, where the descendingmovement of the gas is assumed largely to take place along the verticalwalls. Two other examples are given in U.S. Pat. No. 2,589,956 and U.S.Pat. No. 3,691,731.

An intermediate design is disclosed in U.S. Pat. No. 4,583,999, wherethe washing liquid is supplied horizontally but, probably after somedeceleration, descends as a rain of finely divided droplets.

In a gas washing tower of the type closest the invention in the known"State of the art", e.g. DE-A1 33 41 318 or U.S. Pat. No. 3,532,595,liquid is generally supplied at 4-6 levels. Each level has severalnozzles distributing small droplets within an area generally in the formof a conical shell, hollow-cone type, or within a complete cone,full-cone type. The vertex angle of this cone is 90°-120°.

Each level is provided with nozzles arranged with a spacing of 0.5-1 m,in a regular lattice. The distance between the levels is 1-2 m. At leastsome levels are located far above the bottom of the tower. The purposeof this is that these levels should produce droplets which in the formof a well-distributed rain descend through the tower throughout aconsiderable part of its height.

The efficiency of the gas washer is largely dependent on the relativemovement between the droplets and the gas. It is therefore generallypreferred that the gas flows upwards in a direction contrary to thedescending droplets, i.e. countercurrently, but for various reasonsthere also exist gas washers in which the gas descends in the samedirection as the descending droplets, i.e. concurrently.

If it is desirable to increase the gas washing efficiency when usingthis method, it is necessary either to increase the height of the toweror to increase the flow of washing liquid. Whichever option is chosen,the consequence is increased pump work for a given volume of gas flow.

DESCRIPTION OF THE INVENTION TECHNICAL PROBLEM

Open gas washing towers suffer from the major disadvantage of requitingmuch space. This also entails considerable building costs.

Another drawback, resulting from the former, is that the towers mustnormally be very high. This means that the liquid which is to descendthrough the tower in the form of a rain of fine droplets must first bepumped up to a considerable height. Such pump work has a considerableimpact on the costs of operation.

OBJECT OF THE INVENTION

Gas cleaning and gas cooling in wet-type washers, so-called scrubbers,has for many decades been a well-established technique in processindustries, power plants and incineration plants. This technique is welltried and must be considered both efficient and reliable. The mostobvious drawbacks, which will have been appreciated from the above,reside in that the equipment requires much space, thus becomingexpensive, and much energy, primarily because of the considerable pumpwork.

It therefore is a principal object of the present invention to providean improved method requiring far less bulky gas washing equipment whilemaintaining the reliability and efficiency of known methods.

Another object of the present invention is to provide a method and adevice requiring less energy for gas cleaning and gas cooling.

SUMMARY OF THE INVENTION

The present invention relates to a method for cleaning polluted gasand/or cooling of hot gas, wherein the gas is contacted with finelydivided liquid for the separation of particles or absorption of gaseouspollutants or cooling of the gas. The finely divided liquid is suppliedin the form of essentially umbrella-shaped shells or essentially linearcurtains, in a regular arrangement, distributed in two or more planessubstantially perpendicular to the main flow direction of the gas.

According to the invention, the solution to the contemplated technicalproblem is achieved by supplying the finely divided liquid such that thegas is alternately concentrated and spread by the impulse action exertedby the liquid on the gas in directions perpendicular to the main flowdirection of the gas.

The orthogonal distance between adjacent planes in which finely dividedliquid is supplied, is so adjusted that no substantial equalisation ofthe gas flow takes place between the planes,

The supply of liquid in adjacent planes is so arranged that it, in aplane located downstream in the flow direction of the gas, takes placewhere the flowing gas has been concentrated by the impulse action ofliquid supplied in the plane located immediately upstream.

GENERAL DESCRIPTION OF THE INVENTION

In the following description, the term "tower" is synonymous with"washing tower", and the term "liquid" is synonymous with "washingliquid". The term "gas" means both incoming gas, polluted gas or hotgas, and gas being cleaned or cooled in the contact section.

In the method of the invention, the gas is supplied with finely dividedliquid from regularly arranged supply means. These means are referred tobelow as nozzles, and may be of various designs. The most general typeis a means supplying, around a substantially cylindrical body, finelydivided liquid within a hollow cone, like an umbrella-shaped shell, oran elongate means supplying, along a substantially straight line, finelydivided liquid as a curtain generated by an imaginary motion of thisline.

The nozzles are so arranged that the finely divided liquid, when beingsupplied, imparts to the gas a motion sideways, i.e. transversely of themain flow direction of the gas, thereby producing a concentrationeffect. The nozzles generally supply liquid in a direction, having itsmain component, perpendicular to the direction of the main flow of thegas through the scrubber. The nozzles may be oriented to spray in oneand the same direction in a full plane and in the opposite direction inthe next plane, but preferably all the planes are provided withcircular-spraying umbrella-forming nozzles or with linear nozzlesdistributing liquid in at least two opposite directions.

By means of nozzles arranged in a lattice, supplying liquid indirections substantially perpendicular to the main flow direction of thegas, a displacement and a concentration of the gas are brought aboutsuch that substantially the entire flow passes through the plane inareas that are not adjacent any nozzle. With equal spacing between thenozzles, this area is located around the centre of gravity of thesurface defined by the connecting lines between adjacent nozzles.

According to the invention, in a plane downstream of the first, as seenin the direction of the flowing gas, the nozzles should be disposedopposite these centres of gravity. Furthermore, the planes should belocated so close that there will not be sufficient space or time for thegas flow to be equalised to any major extent before the gas comes intocontact with the finely divided liquid from the nozzles in the nextdownstream plane.

Downstream of this second plane, there are similarly arranged a thirdplane, a fourth plane and so on, as required. A zigzag-like motionthrough the contact section is thus imparted to the gas.

The distance between the planes should be adapted to the nozzle design,such that the liquid supplied in one plane does not interact to asubstantial extent with a contrary flow of liquid from adjacent nozzlesin the adjacent planes. This distance should however be so small thatcompletely droplet-free areas are avoided as far as possible. Thedistance shall be less than 1 m, preferably less than 0,6 m.

As a measure of the interaction may be indicated that part of thedroplets from a nozzle in a certain plane which encounters a higherconcentration or droplet flow density from the adjacent nozzle in anadjacent plane. In the points of space where this takes place, thedroplet flow density, seen as a distribution in the space transverselyof the droplet flow, should have dropped at least to 10% of the maximumvalue at the distance in question from the nozzle.

Since the efficiency depends on the intensity of the contact between thegas and the liquid, the distance between the planes and the dropletdistribution of the nozzles should however preferably be so adjustedthat a minor interaction takes place. A small amount of the dropletsfrom one nozzle should thus come into contact with a small amount fromsaid adjacent nozzle. According to the invention, at least 0.01%,preferably at least 0.1% of the maximum droplet flow density, shouldexist where a hypothetical boundary line between the flows is drawnwhere the two flows have equal density.

If only two planes with nozzles are used, the cone angle of the"umbrella" can be arbitrarily selected for the first plane, while, forthe second plane, it is so adjusted that the umbrellas from the twoplanes are nominally tangent to each other. If several planes of nozzlesare required, it is advantageous to supply the liquid substantially inthe plane, i.e. with a 180° cone angle. This gives a simple symmetry.Also in the case of only two planes, this angle could be the mostadvantageous.

The distribution of nozzles in one plane is advantageously in the formof a regular lattice. If all the planes are to be equipped equally, thesquare structure is the most advantageous. Using a lattice ofequilateral triangles would however not entail any considerabledrawbacks, even if the planes must then be different pairwise. Alsorhombic lattices and, as mentioned, completely rectilinear parallelnozzles may be readily used.

To achieve the advantages of the invention, the number of lattice pointsin each plane should be relatively large, at least 16, preferably atleast 25. In the case of linear nozzles, at least 5 nozzles should beused in each plane.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to theaccompanying drawings, in which

FIG. 1 is a vertical section of a washing tower of conventional design.

FIG. 2 is a vertical section of a washing tower according to the presentinvention.

FIG. 3a shows a suggested distribution of nozzles in planes 81 and 83 ofa washing tower of circular cross-section having a plan according toFIG. 2.

FIG. 3b shows a suggested distribution of nozzles in planes 82 and 84 ofthe washing tower of FIG. 3a;

FIG. 4 shows an alternative distribution of nozzles in a washing towerof circular cross-section.

FIG. 5 shows in more detail the distribution of liquid droplets aroundsome nozzles.

FIG. 6 shows the droplet flow density distribution as a function of aspace coordinate for the nozzles in FIG. 5.

FIG. 7a shows a suggested distribution of nozzles in planes 81 and 83 ofa washing tower of square cross-section having a plan according to FIG.2,

FIG. 7b shows a suggested distribution of nozzles in planes 82 and 84 inthe washing tower of FIG. 7a;

FIG. 8 schematically shows the gas flow through a washing toweraccording to the invention.

FIG. 9a shows the distribution of liquid droplets around linear spraynozzles in an alternative design; and,

FIG. 9b shows a distribution of liquid droplets around hollow-cone typenozzles in an alternative design.

DETAILED DESCRIPTION

FIG. 1 schematically shows a known washing tower 1a having an inlet 2for polluted gas, an outlet 3 for cleaned gas, and an intermediatecontact section 4. In the bottom part 5 of the washing tower 1a, washingliquid 6 is collected. The washing liquid 6 is pumped by a pump 7 up todistributing pipes 8, with nozzles 9a arranged in the upper part of thecontact section 4. The difference in level between the planes 81-84 withnozzles 9a is approximately 2 m. The nozzles 9a, which are shown highlyschematically, are of the hollow-cone type, i.e. they spray finelydivided washing liquid within a conical shell having a 120° vertexangle. The washing liquid then descends as a rain of fine dropletsthrough the contact section and is collected in the bottom part 5. Overthe distributing pipes 8 and the nozzles 9a, there is provided a dropletseparator 10. Fresh washing liquid can be supplied through a conduit 18,and spent polluted washing liquid can be removed through another conduit19.

FIG. 2 shows, also schematically, a tower 1 designed in accordance withthe present invention. This tower 1 differs from that shown in FIG. 1 byits essentially reduced height. Further, the contact section 4 isprovided with nozzles 9 spreading finely divided liquid substantiallyhorizontally, i.e. as a hollow-cone nozzle having a vertex angle of180°. In this case, the difference in level between the planes withnozzles is only 20-60 cm. For greater clarity, the drawing is in thisrespect not to scale, the actual difference in height between the tower1a in FIG. 1 and the tower 1 in FIG. 2 being greater than as isschematically shown. The pans of FIG. 2 corresponding to FIG. 1 bear thesame reference numerals.

FIGS. 3a and 3b show in a practical application the distribution ofnozzles 9 over the cross-section of a tower having circularcross-section. The tower has a diameter of about 12 m and interiorlyaccommodates about 100 nozzles, in each plane, in a square latticepattern with a pitch of about 1 m. The distribution is indicated by thecircles 31, illustrating how the finely divided liquid 6 is sprayed ateach lattice point. FIG. 3a thus shows the distribution of the nozzles 9in the planes 81 and 83 in FIG. 2, and FIG. 3b shows the correspondingdistribution of the nozzles in the planes 82 and 84.

To avoid that a small part of the gas may be passing almostrectilinearly through the tower along the walls, the nozzle distributionof FIG. 4 may be considered. Here, the entire tower circumference isequipped with nozzles 9 oriented inwards and spraying liquidsubstantially in a semicircle, and the distribution of nozzles 9 withinthe tower has been adjusted to this. As appears, the pattern does notbecome completely regular, and the distribution of the nozzles in thenext plane must be adjusted in a manner slightly deviating from thetheoretically desired one.

FIG. 5 shows in more detail how the nozzles 9 in two adjacent planes arearranged in relation to each other and within which area the finelydivided liquid is supplied, through an imaginary vertical sectiondiagonally through the patterns in FIG. 3. To facilitate theunderstanding of the invention, the scale has been distorted byincreasing the distances in the vertical direction in relation to thedistances in the horizontal plane.

From a nozzle 51 in the plane 81 finely divided liquid comes in a flow61. From a nozzle 52 in the plane 82 a contrary flow 62 comes. The flows61 and 62 are not limited by the indicated flow lines 511, 512 and 521,522, which mark the boundaries within which the main parts of the flowsare located. The flows interfere partially with each other, and theboundary where they are substantially equally large is indicated by aline 66. Here, the droplet flow density is however substantially lessthan in the central portion.

FIG. 6 gives an example of the density distribution of the droplet flowin FIG. 5 in a section taken along the line 65. By "droplet flowdensity" is here meant mass flow per unit area. From this Figure appearsthe successive decrease of the flow with increasing distance from therespective plane. As mentioned, the line 66 indicates the boundary ofthe areas where the respective droplet flow is the predominant one.

According to the invention, the distance between the planes 81 and 82should be adapted to the distribution of finely divided liquid such thatthe droplet flow densities 61 and 62 at the boundary line 66 both fallbelow 10% of the maximum value existing close to the respective plane81, 82. However, for optimal utilisation of the advantages of theinvention, it is however assumed that the distance between the planes81, 82 does not become too large. Therefore, the droplet flow densities61, 62 should exceed 0.01% of the maximum value at the boundary line 66,preferably exceed 0.1% of the maximum value.

FIG. 7a and 7b show in a practical application the distribution ofnozzles 9 over the cross-section in a tower having square cross-section.The square has a side of approximately 12.4 m and interiorlyaccommodates about 100 nozzles, in each plane, in a square latticepattern with a pitch of about 1.2 m. The distribution is indicated bythe circles 71 illustrating how the finely divided liquid 6 is injectedat each lattice point. FIG. 7a thus shows the distribution of thenozzles 9 in the planes 81 and 83 in FIG. 2, and FIG. 7b shows thecorresponding distribution of the nozzles in the planes 82 and 84. FIG.7a and 7b show that a square cross-section need not entail anydeviations from the theoretically desired regular lattice.

FIG. 8 schematically shows how the gas flows through the contact section4. The flow lines 11 are meandering around the nozzles 9.

FIG. 9a and 9b show schematically the distribution of liquid dropletsaround some nozzles 9d, 9a having a spraying vertex angle of 120°. InFIG. 9a some linear spraying nozzles 9d is shown which are generatingtwo linear curtains each with an intermediate angle of 120°. As can beseen the planes 81-84 may be pair-wise on the same level or even thatthe gas may first meet the liquid from the later plane. In FIG. 9b thesame pattern is shown when applying hollow-cone type of nozzles 9a. Inthis design it is advantageous to accept a pair-wise difference in thedistance between the liquid droplet flows to accomodate for thedeviation from full symmetry.

The device in FIG. 2 operates as follows. Gas enters the tower 1 throughthe inlet 2 to the contact section 4. It ascends substantiallyvertically as indicated by arrow 41 until it comes to the vicinity ofthe first plane 81 with nozzles 9.

Through the nozzles 9, liquid 6 is injected substantially horizontallyinto the gas at a rate of 10-15 m/s. The gas is affected by the finelydivided liquid and is entrained thereby in a direction which isapproximately horizontal until it encounters other gas flowing in theopposite direction substantially midway between the nozzles 9 in thesame plane 81.

Since the liquid droplets here have a substantially lower droplet flowdensity than close to the nozzle 9 (for they are naturally spread over alarger volume with increasing distance), the gas passes between theliquid droplets upwards towards the next plane 82 straight opposite anozzle 9 in this second plane. The gas flow thus concentrated by theimpulse of the washing liquid in the plane 81 is there spread by theimpulse of the liquid droplets injected into the gas by this nozzle 9.The gas flows, also there, substantially horizontally until itencounters gas entrained by the liquid droplets from adjacent nozzles 9.

This procedure is then repeated at the passage to the plane 83 and soon. By the repeated deflection and the alternating acceleration andretardation, there is produced an intense and efficient interactionbetween gas and liquid.

Liquid which in the form of finely divided droplets is entrained by thegas is separated in the droplet separator 10.

Through the conduit 19, a portion of the liquid is drained forsubsequent treatment, and fresh or regenerated liquid is suppliedthrough the conduit 18, as required.

The method according to the invention is of course not restricted to theembodiment described above but may be modified in several different wayswithin the scope of the appended claims.

As mentioned above, nozzles of various designs can be used. Also, thenozzles can be arranged in many different ways. Regular lattices arepreferred but deviations therefrom are readily conceivable. Triangularor rhombic lattices may give very good results. An advantageousalternative is to equip every other plane with nozzles arranged in atriangular lattice and every other with nozzles arranged in a hexagonallattice.

Moreover, the method may of course be used other than for cleaningpolluted gases or cooling of hot gases. It may advantageously be appliedin most contexts where a gas is to be contacted with a finely dividedliquid.

I claim:
 1. A method for contacting a gas with a finely divided liquidfor at least one of a separation of particles, adsorption of gaseouspollutants, and cooling of the gas, comprising the steps of:injecting afinely divided liquid in the form of a plurality of umbrella-shapedshells or linear curtains, in a regular arrangement, into a gas flow,the finely divided liquid being distributed in at least two supplyplanes substantially perpendicular to a main flow direction of the gaswherein a substantial portion of the finely divided liquid is injectedwith a velocity component in a plane perpendicular to the main flowdirection of the gas that is greater than a velocity component parallelto or contrary to the main flow direction of the gas, wherein the finelydivided liquid provides an impulse action on the gas flow deflecting thegas flow from the main flow direction so that the gas is alternatelyconcentrated and spread in directions perpendicular to the main flowdirection of the gas, an orthogonal distance between adjacent supplyplanes in the main flow direction being set so that the gas flow is notallowed to equalize between adjacent supply planes, and wherein liquidis injected in positions in adjacent supply planes so that the injectionof liquid in a plane located downstream in the main flow direction ofthe gas takes place where the gas flow has been concentrated by theimpulse action of liquid supplied in a plane located immediatelyupstream in the main flow direction.
 2. A method as claimed in claim 1,wherein the orthogonal distance between adjacent planes in which finelydivided liquid is supplied is set so that no substantial interactionbetween droplets supplied in different planes takes place betweendroplets flowing in opposite directions.
 3. A method as claimed in claim2, wherein the orthogonal distance between adjacent planes in whichfinely divided liquid is supplied is set so that an overlap area betweenadjacent contrary flows of droplets supplied in different planesprovides equal density in the adjacent contrary flows at points where adensity of liquid in each respective contrary flow is between 0.01% and10% of a maximum density.
 4. A method as claimed in claim 3, wherein theorthogonal distance between adjacent planes in which finely dividedliquid is supplied is set so that interaction between adjacent contraryflows of droplets supplied in different planes does not take placebetween a main portion of the respective contrary droplet flows in anarea immediately between supply points for the adjacent contrary flows.5. A method as claimed in claim 2, wherein the orthogonal distancebetween adjacent planes in which finely divided liquid is supplied isset so that interaction between adjacent contrary flows of dropletssupplied in different planes does not take place between a main portionof the respective contrary droplet flows in an area immediately betweensupply points for the adjacent contrary flows.
 6. A method as claimed inclaim 2, wherein a main portion of the finely divided liquid is injectedin a direction contained within an angle of 20° symmetrical about aplane perpendicular to the main flow direction of the gas.
 7. A methodas claimed in claim 2, wherein a main portion of the finely dividedliquid is injected as an hollow-cone with a vertex angle of 90° to 180°and with an axis of symmetry essentially parallel to the main flowdirection of the gas and by arranging the nozzles in adjacent planes forantiparallel injection.
 8. A method as claimed in claim 1, wherein theorthogonal distance between adjacent planes in which finely dividedliquid is supplied is set so that an overlap area between adjacentcontrary flows of droplets supplied in different planes provides equaldensity in the adjacent contrary flows at points where a density ofliquid in each respective contrary flow is between 0.01% and 10% of amaximum density.
 9. A method as claimed in claim 8, wherein a mainportion of the finely divided liquid is injected in a directioncontained within an angle of 20° symmetrical about a plane perpendicularto the main flow direction of the gas.
 10. A method as claimed in claim8, wherein a main portion of the finely divided liquid is injected as anhollow-cone with a vertex angle of 90° to 180° and with an axis ofsymmetry essentially parallel to the main flow direction of the gas andby arranging the nozzles in adjacent planes for antiparallel injection.11. A method as claimed in claim 1, wherein the orthogonal distancebetween adjacent planes in which finely divided liquid is supplied isset so that interaction between adjacent contrary flows of dropletssupplied in different planes does not take place between a main portionof the respective contrary droplet flows in an area immediately betweensupply points for the adjacent contrary flows.
 12. A method as claimedin claim 11, wherein a main portion of the finely divided liquid isinjected in a direction contained within an angle of 20° symmetricalabout a plane perpendicular to the main flow direction of the gas.
 13. Amethod as claimed in claim 1, wherein a main portion of the finelydivided liquid is injected in a direction contained within an angle of20° symmetrical about a plane perpendicular to the main flow directionof the gas.
 14. A method as claimed in claim 1, wherein a main portionof the finely divided liquid is injected as an hollow-cone with a vertexangle of 90° to 180° and with an axis of symmetry essentially parallelto the main flow direction of the gas and by arranging the nozzles inadjacent planes for antiparallel injection.
 15. A method as claimed inclaim 1, wherein the orthogonal distance between adjacent planes inwhich finely divided liquid is supplied is adjusted so that an overlaparea between adjacent contrary flows of droplets supplied in differentplanes provides equal density in the adjacent contrary flows at pointswhere a density of liquid in each respective contrary flow is between0.1% and 10% of a maximum density.
 16. A method as claimed in claim 1,wherein a main portion of the finely divided liquid is injected in adirection contained within an angle of 10° symmetrical about a planeperpendicular to the main flow direction of the gas.
 17. A device forcontacting a gas with a finely divided liquid for at least one of aseparation of particles, adsorption of gaseous pollutants, and coolingof the gas, comprising;an inlet for a gas flow, an outlet for treatedgas, a contact section disposed between the inlet and the outlet throughwhich the gas flows in a main flow direction and supply means disposedin the contact section for injecting finely divided liquid in the formof essentially umbrella-shaped shells or essentially linear curtains,the supply means being disposed in at least two planes substantiallyperpendicular to the main flow in an essentially regular latticepattern, the supply means being adapted to supply a substantial portionof the finely divided liquid having a velocity component in a planeperpendicular to the main flow direction greater than a velocitycomponent parallel to or contrary to the main flow direction and beingpositioned to inject finely divided liquid into the flow so that the gasis alternately concentrated and spread by an impulse action exerted bythe liquid on the gas in directions perpendicular to the main flowdirection of the gas, wherein an orthogonal distance between adjacentplanes of supply means is sufficiently small so that no substantialequalisation of the gas flow takes place between planes, and wherein thesupply means in adjacent planes are positioned so that supply means in aplane located downstream in the flow direction of the gas are locatedwhere the gas flow has been concentrated by the impulse action of liquidsupplied in the plane located immediately upstream.
 18. A device asclaimed in claim 17, wherein the orthogonal distance between adjacentplanes is substantially less than a distance between adjacent latticepoints or adjacent lines in adjacent planes and that the orthogonaldistance between adjacent planes with supply means is less than 1 m. 19.A device as claimed in claim 18, wherein the supply means comprisessubstantially circular-spraying nozzles arranged in a lattice of one ofa substantially triangular, quadrangular, hexagonal and equilateralpattern and wherein lattice patterns in adjacent planes are relativelystaggered so that lattice points in a plane located downstream, as seenin tile main flow direction of the gas, are located substantiallystraight opposite the centres of gravity of the polygons generated bylines between adjacent lattice points in a plane located immediatelyupstream.
 20. A device as claimed in claim 18, wherein the supply meanscomprise substantially rectilinear nozzles, the lines are straight andsubstantially parallel, and uniformly distributed over a cross-sectionof a contact portion and that the lines in adjacent planes are offset sothat they are positioned, in a plane located downstream as seen in themain flow direction of the gas, substantially straight opposite animaginary centre line midway between adjacent lines in the plane locatedimmediately upstream.
 21. A device as claimed in claim 17, wherein thesupply means comprise substantially circular-spraying nozzles arrangedin a lattice of one of a substantially triangular, quadrangular,hexagonal and equilateral pattern and wherein lattice patterns inadjacent planes are relatively staggered so that lattice points in aplane located downstream, as seen in the main flow direction of the gas,are located substantially straight opposite the centres of gravity ofthe polygons generated by lines between adjacent lattice points in aplane located immediately upstream.
 22. A device as claimed in claim 17,wherein the supply means comprise substantially rectilinear nozzles, thelines are straight and substantially parallel, and uniformly distributedover a cross-section of a contact portion and that the lines in adjacentplanes are offset so that they are positioned, in a plane locateddownstream as seen in the main flow direction of the gas, substantiallystraight opposite an imaginary centre line midway between adjacent linesin the plane located immediately upstream.
 23. A device as claimed inclaim 17, wherein the orthogonal distance between adjacent planes issubstantially less than a distance between adjacent lattice points oradjacent lines in adjacent planes and that the orthogonal distancebetween adjacent planes with supply means is less than 0.6 m.